Yes, the 02 sensor can be bad and NOT throw a code. Recently I was having an issue with my 98 where it would bog, hesitate and miss at about 2500 to 4000 rpm . I changed plus, new cap, cleaned TB and checked reference on the TPS with zero results. While my throttle response was stellar, the issue was still there.
On a lark I unplugged the front 02 sensor and boom, issue solved. Obviously it threw a CEL once it was unplugged, but the rough run issue was solved. New 02 sensor and it's back to running great. It may have been that the 02 sensor wasn't outside the parameters enough to throw a CEL but bad enough to cause the issue.
Hope this helps.